Re-CAPTCHA anti spam

I have just installed the Wordpress plugin from the guys at Re-Captcha as part of my ongoing attempt at blocking spam. For those of you who do not know a CAPTCHA (or Completely Automated Turing Test To Tell Computers and Humans Apart) are the little images you see on the end of forms with blurred and distorted sequences that you have to enter to correctly complete the form. It is an anti-spam technique as these tests are supposed to prevent automated spamming software from completing the forms meant for humans.

As a Wordpress user, I use Askimet as my main anti spam techinque, however I wanted to augment this with a CAPTCHA for a bit more security. I heard about re-Captcha in an article or blog post somewhere and think it is great. It uses the same principles of a CAPTCHA and puts it to good use helping to digitise books. The digitalisation of books (particularly those from before the digital age) uses Optical Character Recognition to parse a scanned image of a book into its constituent letters and words. However OCR is not perfect particularly when the scanned characters are distorted or not uniform. This is why a CAPTCHA is a good anti spam technique (at least for now!).

The digitalisation has many many unknown words and re-Captcha helps solve this. This special CAPTCHA gives you two distorted words, 1 known word and 1 unknown word. The likelihood of a person entering both words correctly increases dramatically if you enter the known word correctly making this an ideal way to help in the digitalisation of books. Add a comment to see the CAPTCHA in action and visit re-captch for your own plugin at http://recaptcha.net.